switch statement in plpgsql

Hello,

Is it possible to use a case switch statement in a plpgsql function or must
I use If-Else statements only?

If so what is the format?

I have tried the following which when compiled is accepted but when I call
the function it crashes.

switch(tregion)

{

case : ''San Ramon'' then tregion := ''San Ramon, CA'';

break;

}